mj2_video_source::get_num_frames

Overrides kdu_compressed_video_source::get_num_frames

Returns the total number of frames in the track. In the case of an interlaced track ( get_field_order returns one of KDU_FIELDS_TOP_FIRST or KDU_FIELDS_TOP_SECOND), there are two images (fields) in every frame; this function returns the number of frames, not the number of images.